I messed around with ltrace to debug the scrollbar delay within dillo fltk-1.3 port. Here's what I get so far. roger@localhost1 ~ $ ltrace -c -p 11442 % time seconds usecs/call calls function ------ ----------- ----------- --------- -------------------- 18.32 0.291790 6785 43 _ZN8Fl_Group4drawEv 11.69 0.186144 1861 100 _ZN7Fl_Tabs6handleEi 9.70 0.154394 8126 19 _ZN9Fl_Window5flushEv 9.41 0.149853 7887 19 _ZN9Fl_Window4drawEv 9.05 0.144073 7582 19 _ZN7Fl_Tabs4drawEv 8.98 0.142919 793 180 _ZN8Fl_Group6handleEi 6.62 0.105367 115 911 _Znwj 5.82 0.092602 101 911 _ZdlPv 4.82 0.076755 102 746 _ZN2Fl12event_insideEPK9Fl_Widget 2.34 0.037301 153 243 strlen 2.11 0.033615 107 314 malloc 2.06 0.032840 104 314 free 1.81 0.028844 1696 17 _Z9fl_scrolliiiiiiPFvPviiiiES_ 1.49 0.023788 141 168 _ZdaPv 1.11 0.017654 105 168 _Znaj 1.04 0.016517 105 157 __vsnprintf_chk 1.01 0.016079 102 157 _ZN9Fl_Input_5valueEPKc 0.89 0.014229 459 31 _ZN8Fl_Input6handleEi 0.39 0.006271 169 37 _ZNK8Fl_Group10draw_childER9Fl_Widget 0.34 0.005480 103 53 _ZNK8Fl_Group5arrayEv 0.31 0.004997 138 36 _ZNK8Fl_Group12update_childER9Fl_Widget 0.23 0.003682 108 34 _ZN9Fl_Slider11scrollvalueEiiii 0.16 0.002508 192 13 _ZN9Fl_Button4drawEv 0.12 0.001868 116 16 _ZN9Fl_Button6handleEi 0.11 0.001818 106 17 _ZN9Fl_Widget6damageEh 0.02 0.000380 190 2 _ZN6Fl_Box4drawEv 0.02 0.000361 180 2 _ZN8Fl_Input4drawEv 0.01 0.000227 113 2 _ZN9Fl_Window6resizeEiiii ------ ----------- ----------- --------- -------------------- 100.00 1.592356 4729 total roger@localhost1 ~ $ ltrace -c -p 11442 % time seconds usecs/call calls function ------ ----------- ----------- --------- -------------------- 29.26 29.729943 120364 247 _ZN8Fl_Group4drawEv 14.75 14.984334 149843 100 _ZN9Fl_Window5flushEv 14.72 14.952232 149522 100 _ZN9Fl_Window4drawEv 14.69 14.922999 149229 100 _ZN7Fl_Tabs4drawEv 13.48 13.693784 228229 60 _Z9fl_scrolliiiiiiPFvPviiiiES_ 4.09 4.157141 329 12601 strlen 2.28 2.320390 860 2695 _Znwj 2.28 2.317818 860 2695 _ZdlPv 2.15 2.186969 1436 1522 free 0.41 0.421299 141 2982 _ZNK8Fl_Group5arrayEv 0.23 0.238538 126 1884 _ZN2Fl12event_insideEPK9Fl_Widget 0.22 0.220701 147 1500 _ZNK8Fl_Group12update_childER9Fl_Widget 0.19 0.188841 2121 89 _ZN7Fl_Tabs6handleEi 0.18 0.179153 248 720 _ZN8Fl_Group6resizeEiiii 0.18 0.179127 117 1522 malloc 0.16 0.159278 556 286 _ZNK8Fl_Group10draw_childER9Fl_Widget 0.13 0.128988 503 256 _ZN8Fl_Group6handleEi 0.09 0.094990 124 761 __vsnprintf_chk 0.09 0.089326 117 761 _ZN9Fl_Input_5valueEPKc 0.08 0.082873 2762 30 _Z9fl_cursor9Fl_Cursorjj 0.08 0.078284 130 600 _ZN9Fl_Input_6resizeEiiii 0.05 0.048376 115 420 _ZN9Fl_Widget6resizeEiiii 0.04 0.042491 118 360 _Z8fl_widthPKci 0.04 0.036692 136 269 _Znaj 0.03 0.030249 112 269 _ZdaPv 0.02 0.024592 105 233 fl_utf8fwd 0.01 0.013969 194 72 _ZN8Fl_Input4drawEv 0.01 0.013501 112 120 _ZN9Fl_Slider11scrollvalueEiiii 0.01 0.012305 146 84 _ZN8Fl_Input6handleEi 0.01 0.012155 289 42 _ZNK9Fl_Widget10draw_labelEv 0.01 0.007515 121 62 fl_utf8back 0.01 0.007343 174 42 _ZNK9Fl_Widget13draw_backdropEv 0.01 0.006733 112 60 _ZN9Fl_Widget6damageEh 0.00 0.004839 115 42 _ZNK9Fl_Widget8draw_boxE10Fl_Boxtypej 0.00 0.002366 182 13 _ZN9Fl_Button4drawEv 0.00 0.001462 104 14 _ZN6Fl_Box6handleEi 0.00 0.001444 103 14 _ZN9Fl_Button6handleEi 0.00 0.000528 264 2 _ZN6Fl_Box4drawEv 0.00 0.000226 113 2 _ZN9Fl_Window6resizeEiiii ------ ----------- ----------- --------- -------------------- 100.00 101.593794 33631 total